JP2016038995A - Power storage device and method for manufacturing power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device in which an electrode can be positioned with respect to a separator and an electrode improperly positioned can be easily detected, and a method for manufacturing a power storage device.SOLUTION: A power storage device includes an electrode assembly 10 including a positive electrode 20 and a negative electrode 30 laminated with separators 41, 42 being interposed therebetween. A pair of the separators 41, 42 are welded so as to include four corners of the positive electrode 20 with the positive electrode 20 being sandwiched between the pair of the separators 41, 42.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage device having an electrode assembly and a method for manufacturing the power storage device.

  The battery structure of a lithium ion battery includes a laminated type and a wound type. In the laminated type, a plurality of sheets are laminated with a separator interposed between a positive electrode and a negative electrode. Generally, the positive electrode, the negative electrode, and the separator are formed in a rectangular shape. In a lithium ion battery, since it is necessary to prevent a short circuit between a positive electrode and a negative electrode and to prevent lithium precipitation, it is known to increase the size relationship in the order of a positive electrode, a negative electrode, and a separator. Furthermore, it is desirable that the positive electrode be disposed at a desired position between the separators without deviation. In Patent Document 1, an electrode is sandwiched between two separators, the separators are joined to each other, and the movement of the electrodes is restricted at the joined portion. In Patent Document 2, the electrode is wrapped with two separators and fused to form a bag.

JP 2012-59696 A JP-A-10-188938

  However, for example, when the movement of the electrode is restricted at the joint between the separators, when the part of the joint is not joined, the electrode cannot be positioned with respect to the separator. Further, for example, if there is a defect in the manufacturing apparatus, positional deviation may occur in the electrode (positive electrode) wrapped in the separator. Even if the position of the electrode (positive electrode) wrapped in the separator was inappropriate, it could not be easily detected. Therefore, an inappropriate electrode having a positional deviation with respect to the separator is laminated in the next step, and the battery is manufactured. Batteries have an inspection process before shipping, etc., and any defects are detected in the inspection process. However, if a defect is detected at this stage, it is discarded as a defective product on a battery (cell) basis.

  The objective of this invention is providing the electrical storage apparatus which can position an electrode with respect to a separator, and can detect an electrode with an improper position easily, and the manufacturing method of an electrical storage apparatus.

  The invention according to claim 1 is a power storage device having an electrode assembly in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween, wherein a pair of the separators includes the positive electrode and the negative electrode. The gist is that the pair of separators are welded including at least two diagonal corners of the four corners of the one electrode in a state where the one electrode formed in a rectangular shape is sandwiched.

  According to the first aspect of the present invention, the pair of separators are welded so as to include at least two diagonal corners of the four corners of the one electrode formed in a rectangular shape. Can be fixed in a state where one electrode is positioned, and the electrode can be positioned with respect to the separator. Further, at least two corners of the four corners of one electrode are visualized by welding, and an electrode with an inappropriate position can be easily detected.

As described in claim 2, in the power storage device according to claim 1, the pair of separators may be configured to be welded including four corners of the one electrode.
According to a third aspect of the present invention, in the power storage device according to the first or second aspect, the pair of separators may be welded so as to include the periphery of the one electrode.

  According to a fourth aspect of the present invention, there is provided a method for manufacturing a power storage device having an electrode assembly in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween, wherein the positive electrode and the negative electrode are paired with the separator. A welding step of welding the pair of separators including at least two diagonal corners of the four corners of the one electrode in a state where one of the electrodes formed in a rectangle is sandwiched, After the welding step, before laminating the positive electrode and the negative electrode with a separator interposed, the positions of at least two diagonal corners of the four corners of the one electrode visible by the welding are inspected. And an inspection process to be performed.

  According to the invention described in claim 4, in the welding step, the pair of separators 4 of the one electrode is sandwiched between the pair of separators and one electrode formed in a rectangular shape of the positive electrode and the negative electrode. It is welded including at least two diagonal corners. Here, since the pair of separators are welded so as to include at least two corners of the four corners of one electrode, the one electrode can be fixed with the one electrode positioned relative to the pair of separators. The electrode can be positioned with respect to.

  In the inspection process, after the welding process, before laminating the positive electrode and the negative electrode with the separator interposed, positions of at least two diagonal corners of the four corners of one electrode that can be visualized by welding Is inspected. Here, by examining the positions of at least two diagonal corners of the four corners of one of the electrodes that can be visualized by welding, it is possible to easily detect an electrode having an inappropriate position.

  According to the present invention, an electrode can be positioned with respect to the separator, and an electrode with an inappropriate position can be easily detected.

The disassembled perspective view which shows an electrode assembly typically. (A) is a top view which shows the separator which accommodated the positive electrode, (b) is a side view which shows the separator which accommodated the positive electrode. The top view before welding for demonstrating a manufacturing process. The top view for demonstrating a welding area | region. The top view after the welding for demonstrating a manufacturing process. The top view for demonstrating the welding area | region of another example. The top view for demonstrating the welding area | region of another example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, a lithium ion secondary battery as a power storage device has an electrode assembly 10. The electrode assembly 10 is disposed in the case. An electrolyte is injected into the case.

In the electrode assembly 10, the positive electrode 20 and the negative electrode 30 are laminated with a bag-like separator 40 (separators 41 and 42) interposed therebetween.
As shown in FIG. 2, the positive electrode 20 includes a rectangular metal foil 21, and has long sides L1, L3 and short sides L2, L4 (see FIG. 3). The positive electrode 20 has positive electrode active material layers 22 formed on both surfaces of a metal foil 21 as a current collector.

  As shown in FIG. 1, the negative electrode 30 includes a rectangular metal foil 31. The negative electrode 30 has a negative electrode active material layer 32 formed on both surfaces of a metal foil 31 as a current collector. The metal foil 21 of the positive electrode 20 is made of, for example, aluminum, and the metal foil 31 of the negative electrode 30 is made of, for example, copper.

  In addition, a positive electrode tab portion 25 that is punched into a rectangular shape is formed on the metal foil 21 of the positive electrode 20 so as to extend upward. The metal foil 31 of the negative electrode 30 is formed with a negative electrode tab portion 35 that is punched into a rectangle and extends upward at a position different from the positive electrode tab portion 25 in the width direction. An active material layer is not formed on the surfaces of the tab portions 25 and 35.

  The positive electrode 20 is accommodated in the bag-like separator 40 so that the positive electrode tab portion 25 extends to the outside. The bag-shaped separator 40 is composed of a pair (two sheets) of separators 41 and 42. Separator 41, 42 consists of resin (for example, polypropylene). The separators 41 and 42 are porous bodies that are impregnated with an electrolytic solution and have a large number of pores through which ions can pass, and are in the form of a translucent or opaque sheet that is nearly opaque.

  As shown in FIG. 2, the separator 40 (41, 42) is formed in a rectangular shape. The bag-like separator 40 is configured by welding a pair of separators 41 and 42. The pair of separators 41, 42 are welded including the four corners C 1, C 2, C 3, C 4 of the positive electrode 20 with the positive electrode 20 formed in a rectangle sandwiched between the pair of separators 41, 42. Further, the pair of separators 41 and 42 are welded including the periphery of the positive electrode 20. By this welding, the triangular areas Z1, Z2, Z3, and Z4 at the four corners C1, C2, C3, and C4 in the positive electrode 20 and the rectangular area Z5 at the base of the tab portion 25 in FIG. It can be done. In the welding region, the separator 41 and the separator 42 are joined, and the positive electrode 20 is joined to the separators 41 and 42. In this embodiment, the welded portion of the separator in the positive electrode 20 is a coated portion of the active material layer 22.

  Next, in the method for manufacturing a lithium ion secondary battery according to the present embodiment, steps relating to the assembly of the electrode assembly 10 will be described with reference to FIGS. In addition, the manufacturing method of each of the positive electrode 20, the negative electrode 30, and the two separators 41 and 42, and the process of injecting the sealing can into the case of the electrode assembly or the electrolyte after manufacturing the electrode assembly, etc. Since a known method is used, the description is omitted.

  First, the positive electrode 20, the negative electrode 30, and the two separators 41 and 42 are prepared. The positive electrode 20 is formed in a rectangular shape, an active material layer 22 is formed on both surfaces of a metal foil 21 as a current collector, and a tab portion 25 is extended. The negative electrode 30 is formed in a rectangular shape, an active material layer 32 is formed on both surfaces of a metal foil 31 as a current collector, and a tab portion 35 is extended. The two separators 41 and 42 are each formed in a rectangular shape.

The size relationship increases in the order of the positive electrode 20, the negative electrode 30, and the separators 41 and 42, and prevents a short circuit between the positive electrode 20 and the negative electrode 30 and prevents lithium deposition.
Then, as shown in FIG. 3, the positive electrode 20 is sandwiched between a pair of separators 41 and 42.

  In this state, the heater is pressed against the welding area Z10 hatched in FIG. The region Z10 includes the four corners C1, C2, C3, and C4 of the rectangular positive electrode 20 in plan view, and includes the periphery of the four sides L1, L2, L3, and L4 of the rectangular positive electrode 20.

  More specifically, as shown in FIG. 4, the region Z <b> 10 has the same outer edge as the outer edge of the rectangular separators 41 and 42. Further, the inner edge of the region Z10 has four straight portions L10, L11, L12, L13 and four oblique portions L14, L15, L16, L17. The straight line portion L10 extends parallel to the long side L1 of the metal foil 21 on the outer side by a predetermined distance ΔL1 with respect to the long side L1 of the rectangular metal foil 21. The straight line portion L11 extends parallel to the short side L2 of the metal foil 21 on the outer side by a predetermined distance ΔL2 with respect to the short side L2 of the rectangular metal foil 21. The straight line portion L12 extends parallel to the long side L3 of the metal foil 21 on the outer side by a predetermined distance ΔL3 with respect to the long side L3 of the rectangular metal foil 21. The straight line portion L13 extends parallel to the short side L4 of the metal foil 21 on the outer side by a predetermined distance ΔL4 with respect to the short side L4 of the rectangular metal foil 21. Further, the oblique portion L14 extends straight inside the corner C1 of the rectangular positive electrode 20 at the corner portion constituted by the straight portion L10 and the straight portion L11. The oblique portion L15 extends straight inside the corner C2 of the rectangular positive electrode 20 at the corner portion constituted by the straight portion L11 and the straight portion L12. The inclined portion L16 extends straight inside the corner C3 of the rectangular positive electrode 20 at the corner portion constituted by the straight portion L12 and the straight portion L13. The inclined portion L17 extends straight inside the corner C4 of the rectangular positive electrode 20 at the corner portion constituted by the straight portion L13 and the straight portion L10.

  By heating the region Z10 in the pair of separators 41 and 42 by the heater, the pair of separators 41 and 42 are welded around the positive electrode 20 including the four corners C1, C2, C3, and C4 of the positive electrode 20 formed in a rectangle. To do. At this time, by welding including the four corners C1, C2, C3, and C4 which are the reference shape portions of the positive electrode 20, the inside of the bag-like separator 40 (separators 41 and 42) is formed as shown in FIG. The triangular areas Z1, Z2, Z3, and Z4 of the four corners C1, C2, C3, and C4 of the positive electrode 20 and the rectangular area Z5 at the root of the tab portion 25 are visualized, and the areas Z1, Z2, Z3, Z4, and Z5 are visualized. Thus, the positive electrode 20 can be seen.

  Specifically, the triangular region Z1 has a triangular shape due to the long side L1 and the short side L2 of the metal foil 21 and the oblique portion L14 of the region Z10. The triangular region Z2 has a triangular shape due to the short side L2 and the long side L3 of the metal foil 21 and the oblique portion L15 of the region Z10. The triangular region Z3 has a triangular shape due to the long side L3, the short side L4, and the oblique portion L16 of the region Z10. The triangular region Z4 has a triangular shape due to the short side L4 of the metal foil 21, the long side L1, and the oblique portion L17 of the region Z10.

  Further, a portion corresponding to the predetermined distance ΔL1 in FIG. 4, that is, a portion between the straight portion L10 and the long side L1 of the rectangular metal foil 21 at the inner edge of the region Z10 is an unwelded gap AG1. A portion corresponding to the predetermined distance ΔL2 in FIG. 4, that is, a portion between the straight portion L11 and the short side L2 of the rectangular metal foil 21 at the inner edge of the region Z10 is an unwelded gap AG2. A portion corresponding to the predetermined distance ΔL3 in FIG. 4, that is, a portion between the straight portion L12 and the long side L3 of the rectangular metal foil 21 at the inner edge of the region Z10 is an unwelded gap AG3. A portion corresponding to the predetermined distance ΔL4 in FIG. 4, that is, a portion between the straight portion L13 and the short side L4 of the rectangular metal foil 21 at the inner edge of the region Z10 is an unwelded gap AG4.

  In this welding process, the pair of separators 41, 42 are provided at the four corners C 1, C 2. It is welded including C3 and C4. Therefore, the positive electrode 20 can be fixed in a state of being positioned with respect to the pair of separators 41 and 42. As a result, the positive electrode 20 can be positioned with respect to the separators 41 and 42. Moreover, since the circumference | surroundings of the positive electrode 20 are enclosed by a welding part, a position is hard to shift | deviate.

  Moreover, the electrode in the separator can be seen by welding (dissolving) the shape portion serving as a reference for the electrode (positive electrode). That is, when the separators 41 and 42 are welded, in the triangular regions Z1, Z2, Z3, and Z4 at the four corners of the positive electrode 20, the separators 41 and 42 are seen through by melting the resin and crushing the internal pores. It is possible to confirm the positions of the four corners C1, C2, C3, and C4.

  Then, after the welding step, before the positive electrode and the negative electrode are laminated with the separator interposed, the positions of the four corners C1, C2, C3, and C4 of the positive electrode 20 that can be visualized by welding are inspected. Thus, in the inspection process, by inspecting the positions of the four corners C1, C2, C3, and C4 of the positive electrode 20 that can be visualized by welding, the positive electrode 20 having an inappropriate position can be easily detected.

  Thereafter, the positive electrode and the negative electrode are laminated with a separator interposed therebetween to produce an electrode assembly. At this time, it can laminate | stack on the basis of the corner of the positive electrode 20 which confirmed the position. In particular, the corner of the positive electrode 20 is easy to use as a reference.

  For example, when the position of the electrode (positive electrode) wrapped in the separator becomes inappropriate due to a defect in the manufacturing apparatus and the positional deviation of the positive electrode wrapped in the separator occurs, conventionally, it cannot be easily detected, For this reason, an inappropriate electrode in which the positional deviation occurs with respect to the separator is laminated in the next step, and the battery is manufactured. A defect is detected in an inspection process such as before the battery is shipped. If a defect is detected at this stage, the battery is discarded as a defective product on a battery (cell) basis.

  In contrast, in the present embodiment, the position of the positive electrode 20 deviates from the permissible value immediately after the positive electrode 20 positioned with respect to the separators 41 and 42 is welded in a state sandwiched between the separators 41 and 42. Can be detected. Therefore, it is possible to easily detect an inappropriate position of the electrode (positive electrode), and it is possible to prevent the positive electrode 20 (and the separators 41 and 42) having a shifted position from flowing to a subsequent process.

According to the above embodiment, the following effects can be obtained.
(1) As a configuration of a lithium ion secondary battery as a power storage device, a pair of separators 41 and 42 are paired with a pair of separators 41 and 42 sandwiching a positive electrode 20 as one electrode formed in a rectangular shape of a positive electrode and a negative electrode. The separators 41 and 42 were welded including the four corners C1, C2, C3, and C4 of the positive electrode 20. Therefore, since the pair of separators 41 and 42 are welded including the four corners C1, C2, C3 and C4 of the positive electrode 20 formed in a rectangular shape, the positive electrode 20 is positioned with respect to the pair of separators 41 and 42. The positive electrode 20 can be positioned with respect to the separators 41 and 42. Further, the four corners C1, C2, C3, and C4 of the positive electrode 20 are visualized by welding, and the positive electrode 20 having an inappropriate position can be easily detected.

  (2) Further, as a configuration of the lithium ion secondary battery, since the pair of separators 41 and 42 are welded including the four corners C1 to C4 of the positive electrode 20, the positive electrode 20 is more reliably positioned with respect to the separators 41 and 42. can do.

  (3) Further, as a configuration of the lithium ion secondary battery, since the pair of separators 41 and 42 including the periphery of the positive electrode 20 are welded, the positive electrode 20 can be hardly displaced with respect to the separators 41 and 42.

  (4) As a manufacturing method of a lithium ion secondary battery, it has a welding process and an inspection process. In the welding step, the pair of separators 41, 42 is placed in the four corners of the positive electrode 20 with the positive electrode 20 as one electrode formed in a rectangular shape of the positive electrode and the negative electrode sandwiched between the pair of separators 41, 42. Weld including C1, C2, C3 and C4. In the inspection process, the positions of the four corners C1, C2, C3, and C4 of the positive electrode 20 that can be visualized by welding are inspected after the welding process and before the positive electrode and the negative electrode are laminated with the separator interposed therebetween. Therefore, the positive electrode 20 can be positioned with respect to the separators 41 and 42, and the positive electrode 20 whose position is inappropriate can be easily detected.

The embodiment is not limited to the above, and may be embodied as follows, for example.
Although the pair of separators 41 and 42 are welded including the four corners of the positive electrode 20 and the pair of separators 41 and 42 are welded including the periphery of the positive electrode 20, the present invention is not limited to this.

  For example, as shown in FIG. 6, the periphery of four corners C1, C2, C3, and C4 of the positive electrode 20 is set as a welding region Z20, Z21, Z22, and Z23, and a pair of separators 41 and 42 are arranged around the corner of the positive electrode 20. You may make it not weld except a part.

  As shown in FIG. 7, a region including the two diagonal corners C1 and C3 of the positive electrode 20 is a welding region Z30, and the pair of separators 41 and 42 includes the two diagonal corners C1 and C3 of the positive electrode 20. Weld with. Alternatively, the pair of separators 41 and 42 are welded including two diagonal corners C2 and C4 in the positive electrode 20. In addition, a pair of separators 41 and 42 are welded including three corners (for example, corners C1, C2, and C3) of the positive electrode 20.

  In short, the pair of separators 41 and 42 may be welded including at least two of the four corners of the positive electrode 20 with the positive electrode 20 sandwiched between the pair of separators 41 and 42.

  In the above-described embodiment, the welded portion of the separator in the positive electrode 20 is the coated portion of the active material layer 22, but it may be an uncoated portion. Supplementally, in order to prevent lithium precipitation, more precisely, it is preferable to make the area of the negative electrode active material layer larger than the area of the positive electrode active material layer. Therefore, the area of the positive electrode metal foil may be the same as the area of the negative electrode metal foil, and instead, the positive electrode active material layer may be formed to have a smaller area than the negative electrode active material layer. At this time, a positive electrode having a portion where the uncoated metal foil is exposed on the four sides around the positive electrode active material layer. For example, when using such a positive electrode, an uncoated part may be welded to a separator.

  Although the pair of separators 41 and 42 are welded with the positive electrode 20 sandwiched between the pair of separators 41 and 42, the pair of separators 41 and 42 may be welded with the negative electrode sandwiched between the pair of separators 41 and 42. Good.

  -You may apply as an electrical storage apparatus other than a lithium ion secondary battery. For example, the present invention may be applied to a nickel hydrogen secondary battery.

  DESCRIPTION OF SYMBOLS 10 ... Electrode assembly, 20 ... Positive electrode, 30 ... Negative electrode, 41 ... Separator, 42 ... Separator.

Claims (4)

A power storage device having an electrode assembly in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween,
With the pair of separators sandwiching one of the electrodes formed in the rectangular shape of the positive electrode and the negative electrode, the pair of separators is connected to at least two diagonals of the four corners of the one electrode. A power storage device characterized by welding including a corner.   The power storage device according to claim 1, wherein the pair of separators are welded including four corners of the one electrode.   The power storage device according to claim 1, wherein the pair of separators are welded including the periphery of the one electrode. A method of manufacturing a power storage device having an electrode assembly in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween,
With the pair of separators sandwiching one of the electrodes formed in the rectangular shape of the positive electrode and the negative electrode, the pair of separators is connected to at least two diagonals of the four corners of the one electrode. A welding process for welding including a corner;
After the welding step, before laminating the positive electrode and the negative electrode with a separator interposed, the positions of at least two diagonal corners of the four corners of the one electrode visible by the welding are inspected. An inspection process to
A method for manufacturing a power storage device, comprising: